1. Field of the Invention
The present invention relates to a capillary electrophoresis method using an internal standard substance.
2. Description of the Related Art
Capillary electrophoresis is a technique in which a certain voltage is applied across opposite ends of a capillary having an inner diameter of about 100 μm to electrophorese substances in the capillary filled with an electrolytic solution, and the electrophoresed substances are detected using a detector to measure a migration time of each peak from a signal of the detector and identify the peak based on the migration time. In reality, even if electrophoresis conditions, such as applied voltage and temperature, are kept constant, a migration time of each substance generally varies in every migration. These variations cause difficulty in accurately identifying the substance based on only the migration time thereof.
As one solution to this problem, there has been known a technique in which an internal standard substance is added to a sample solution and electrophoresed together with sample components, and a migration time of each peak of the sample components is corrected using a migration time of the internal standard substance as an index, before identification. For example, when a sample component is a DNA or RNA, and it is intended to estimate a size thereof, at least two types of internal standard substances capable of being separated with a certain predetermined resolution and detected in both sides of a molecular weight range (on the side of a low molecular weight and on the side of a high molecular weight: hereinafter referred to respectively as “low-molecular-weight-side (LMW-side) internal standard substance” and “high-molecular-weight-side (HMW-side) internal standard substance”) are added to a sample solution, and a migration time of each peak of the sample components is corrected using respective detection times of the LMW-side and HMW-side internal standard substances as indexes, on a program basis, before estimating a size of an RNA or DNA. In the following Non-Patent Publication 1, a 50-bp double-stranded DNA is used as a LMW-side internal standard substance, and an 800-bp double-stranded DNA is used as a HMW-side internal standard substance.
[Non-Patent Publication 1] Hitachi Chemical Technical Report No. 40 (2003-1)